Information display screen



Oct. 26, 1965 E. A. sAcK 3,214,635

INFORMATION DISPLAY SCREEN Filed April 10, 1962 2 Sheets-Sheet 1 Xl x2 x3 x4 x5 X6 x7 g- 4a a Y4 cs4 e44 Y3 C ,3 X C33 043 C Y2 c Yl u o 6 o u L 5 PRIOR ART Fig.2A. Fig.2B.

4 ELECTROLUMINESCENT Y WITNESSES [M NTO Edgar A. Sock Oct. 26, 1965 E, K 3,214,635

INFORMATION DISPLAY SCREEN 2- Fig.3.

BRIGHTNESS lN ARBITRARY UNITS DC VOLTS Xl X2 X3 X4 X5 X6 X7 LI-l E 20 3 Y6 5 Y5 E V Y4 (D 234 244 Y3 g Z33 243 Y2 [I O I Yl SCANNING APPARATUS VERTICAL SUPPLY SOURCE Fig.4.

United States Patent 3,214,635 INFORMATION DISPLAY SCREEN Edgar A. Sack, Pittsburgh, Pa, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, 21 corporation of Pennsylvania Filed Apr. 10, 1962, Ser. No. 186,533 6 Claims. (Cl. 315-161) The present invention relates to information display screens, and more particularly to information display screens utilizing electroluminescent screen elements.

In information display screens utilizing electroluminescent elements arranged in a matrix of rows and columns, the problem of side lighting or cross lighting arises, wherein neighboring elements as well as the selected elements are excited. This problem arises due to the fact that when the particular row and column of the electroluminescent element desired to be illuminated has applied across it the exciting potential; part of this potential is also applied across other neighboring elements in the matrix. The amount of side or cross lighting may be attenuated by using electroluminescent materials that have a rapidly rising light output with respect to the amount of voltage applied thereto. However, this does not eliminate the problem completely.

It is therefore an object to provide a new and improved information display screen utilizing electroluminescent elements which eliminates the side or cross lighting problem.

It is a further object of the present invention to provide new and improved information display screens utilizing electroluminescent elements which are responsive to direct potential and emit more light when the potential is of one polarity rather than of the other polarity.

Broadly, the present invention provides an information display screen, wherein, a plurality of electroluminescent elements are arranged in a matrix of rows and columns, with the electroluminescent elements having the characteristic to emit more light when a potential of one polarity rather than the other is applied thereto to scan the screen, only the elements desired to emit light have the correct polarity potential applied thereto, while the other rows and columns are maintained at a no light producing polarity.

These and other objects will become more apparent when considered in view of the following specification and drawings, in which:

FIG. 1 is a schematic diagram of an information display screen to show the problem of side lighting in the prior art;

FIG. 2A is a schematic diagram of an electroluminescent screen element which may be utilized in the present invention;

FIG. 2B is a symbolic diagram of the element of FIG. 2A;

FIG. 3 is a plot of the brightness vs. voltage characteristic of the screen element of FIG. 2; and

FIG. 4 is a schematic diagram of an information display screen utilizing the teachings of the present invention.

Referring to FIG. 1, the problem of side lighting is exemplified in a display screen of the prior art. Arranged in the screen matrix of rows Y1 through Y7 and the columns X1 through X7 are alternating current electroluminescent elements to form a cross grid screen pattern. For purposes of illustrating the problem, only the screen elements C44, C43, C33 and C34 are shown. It, for example, the screen element C44 is desired to be illuminated, the AC. source is connected between the row Y4 and the column X4; thus placing an alternating potential V across the screen element C44, and exciting the electroluminescent element C44 to its illuminating state. However, it should be noted that the potential V also appears across the parallel path including the screen elements. C34, C33 and C43; with each of these elements receiving one-third of the AC. source potential V. Depending upon the light vs. voltage characteristic of the particular electroluminescent elements used, a certain amount of light, somewhat diminished from the light emitted from the element C44, will be emitted from the neighboring electroluminescent elements C34, C33 and 43, and also other from neighboring elements in the matrix which have a portion of voltage V impressed thereacross. Hence, with the neighboring elements also emitting light along with the desired element C44, the definition of the screen may be severely hampered. It should be also recognized that the same problem would exist if D.C. electroluminescent elements, which are symmetrically responsive to direct current in either direction, were used.

In FIG. 2A there is shown an electroluminescent cell 2, exhibiting desired characteristics which may be incorporated into the screen of the present invention. The electroluminescent cell 2 comprises: a glass foundation 4; a light-transmitting, electrical conducting layer of tin oxide 6 contiguous to the glass layer 4; an electroluminescent layer 8 of yellow zinc sulphide phosphor activated by copper and manganese and coactivated by chlorine carried by the tin oxide layer 6; and a vacuum metallized aluminum electrode 10 carried over the phosphor thin film 8. The row terminal Y is connected to the tin oxide layer 6, and the column terminal X is connected to the metal electrode 10.

The method of preparing the electroluminescent element of FIG. 2 is described in U.S. Patent 3,044,902, by W. Thornton, issued July 17, 1962, and assigned to the assignee of the present invention.

The brightness vs. voltage characteristic of the electroluminescent element of FIG. 2A is shown in FIG. 3. From this plot it can be seen that with one terimnal, for example the terminal Y, being positive with respect to the other terminal, in this case terminal X, of FIG. 2, the brightness increases with increasing positive voltages. However, in the negative direction, with the terminal X positive with respect to the terminal Y, there is substantially no light'emitted from the cell. FIG. 2B shows a symbolic circuit of the electroluminescent cell of FIG. 2A. The analogy of FIG. 2B being that more light is emitted from the cell 2' when current readily flows from terminal Y to terminal X when a potential of a polarity making terminal Y positive with respect to X is applied across the cell, and substantially no light is emitted from the cell 2 when a direct voltage of the opposite polarity is applied across the terminals X and Y.

FIG. 4 shows electroluminescent elements of the type shown in FIG. 2A connected in a matrix array of rows Y1 through Y7 and columns X1 through X7. Only the screen elements Z44, Z34, Z33 and'Z43 are shown for purposes of explanation. The horizontal supply source 20 is connected to the rows Y1 through Y7, and the vertical supply source 22 is connected to the columns X1 through X7 of the matrix. The rows Y1 through Y7 are normally maintained at a negative potential by the horizontal supply source 20, and the columns X1. through X7 are normally maintained at a positive potential by the vertical supply source 22. If it is desired to illuminate a particular screen element, for example element Z44, the polarity of the potential of the row and column of the desired element is reversed. That is, the polarity of the row X4 is changed to plus and the polarity of the column Y4 is changed to minus. With the row Y4 positive with respect to the column X4 the element Z44 will emit light according to the characteristic of FIG. 3 in the positive direction. However, all other elements of the array would not have the correct potential applied in order to emit any substantial amount of light. For example, the element Z34 will be connected from a positive potential to a positive potential; thus will have zero potential across it and will emit substantially no light. The element Z43 will be connected from a minus potential to a minus potential and will likewise emit no light. The element Z33 will be connected from a minus potential at the row Y3 to a plus potential at the column X3, which will maintain this element in its negative region and therefore can emit no light. The remaining elements in the array also will be in the condition that either no voltage appears across the element or that a voltage of the wrong polarity appears thereon, such that, only the element Z44 desired to emit light will be illuminated.

The scanning apparatus 24 is connected to the horizontal supply source and the vertical supply source 22 so that the screen array may be scanned and any of the elements illuminated as desired. Such scanning apparatus, such as a series of switches, and supply sources are well known in the art and will not be described further herein. The essential factor is that the rows be maintained at one polarity and the columns at the other polarity. When it is desired to illuminate an element, the polarity of the potential thereacross is reversed.

Although the present invention has been described with a certain degree of particularity, it should be understood that the present disclosure has been made only by way of example and that numerous changes in the details of fabrication and the combination and arrangement of parts may be resorted to without departing from the scope and the spirit of the present invention.

I claim as my invention:

1. In an information display screen, the combination of: a plurality of screen display elements operative to emit light, said screen elements having the characteristic to emit a substantial quantity of light when a direct potential of one polarity is applied thereto and substantially no light when a potential of the other polarity is applied thereto; and control means selectively to apply direct potentials of the polarity to emit light to screen elements selected to emit light, while maintaining the potential across non-selected elements at the other polarity so as not to emit light.

2. In an information display screen, the combination of: a plurality of screen display elements operative to emit light and being arranged in a matrix of rows and columns, each of said screen elements having the characteristic to emit a substantial quantity of light when a direct potential of one polarity is applied thereto and substantially no light when a potential of the other polarity is applied thereto; and control means selectively to apply direct potentials of the polarity to emit light across rows and columns of screen elements selected to emit light, while maintaining the potential across the other rows and columns of non-selected elements at the other polarity so as not to emit light.

3. In an information display screen, the combination of: a plurality of electroluminescent screen display elements operative to emit light and being arranged in a matrix of rows and columns, each of said screen elements comprising a thin film of electroluminescent material being responsive to emit a substantial quantity of light when a direct potential of one polarity is applied thereto and substantially no light when a potential of the other polarity is applied thereto; and control means selectively to apply direct potentials of the polarity to emit light across rows and columns of screen elements selected to emit light, while maintaining the potential across the other rows and columns of non'selected elements at the other polarity so as not to emit light.

4. In an information display screen, the combination of: a plurality of electroluminescent screen display elements operative to emit light and being arranged in a matrix of rows and columns, each of said screen elements being responsive to emit a substantial quantity of light when a direct potential of one polarity is applied thereto and substantially no light when a potential of the other polarity is applied thereto; supply means normally to maintain the rows of said matrix at one polarity of direct potential and the columns of said matrix at the other polarity, with the polarity of the potential across said screen elements being such that said elements normally emit substantially no light; and scanning means selectively to reverse the polarity of direct potential across the rows and columns of selected of said elements to emit light, while maintaining the potentials established by said supply means on the non-selected rows and columns.

5. In an information display screen, the combination of: a plurality of electroluminescent screen display elements operative to emit light and being arranged in a matrix of rows and columns, each of said screen elements comprising a thin film of electroluminescent material being responsive to emit a substantial quantity of light when a direct potential of one polarity is applied thereto and substantially no light when a direct potential of the other polarity is applied thereto; supply means normally to maintain the rows of said matrix at one polarity of direct potential and the columns of said matrix at the other polarity, with the polarity of the potential across said screen elements being such that said screen elements normally emit substantially no light; and scanning means selectively to reverse the polarity of direct potential across the rows and columns of selected of said screen elements to emit light, while maintaining the potentials established by said supply means on the non-selected rows and columns.

6. In an information display screen, the combination of: a plurality of electroluminescent screen display elements operative to emit light and being arranged in a matrix of rows and columns, each of said screen elements comprising a thin film of electroluminescent phosphor material being responsive to emit substantially more light when a direct potential of one polarity is applied thereto rather than the other polarity; supply means operatively connected to the rows and columns of said matrix and being operative normally to maintain the rows of said matrix at one polarity of direct potential and the columns of said matrix at the other polarity, with the polarity of the potential across said screen elements being such that said elements normally emit substantially no light; and

scanning means operatively connected to said supply means selectively to reverse the polarity of direct potential across the rows and columns of selected of said elements to emit light, while maintaining the potentials established by said supply means on the non-selected rows and columns.

References Cited by the Examiner UNITED STATES PATENTS JOHN W. HUCKERT, Primary Examiner.

EDWARD v. BENHAM, DAVID J. GALVIN,

E m ne s. 

1. IN AN INFORMATION DISPLAY SCREEN, THE COMBINATION OF: A PLURALITY OF SCREEN DISPLAY ELEMENTS OPERATIVE TO EMIT LIGHT, SAID SCREEN ELEMENTS HAVING THE CHARATERISTIC TO EMIT A SUBSTANTIAL QUANTITY OF LIGHT WHEN A DIRECT POTENTIAL OF ONE POLARITY IS APPLIED THERETO AND SUBSTANTIALLY NO LIGHT WHEN A POTENTIAL OF THE OTHER POLARITY IS APPLIED THERETO; AND CONTROL MEANS SELECTIVELY TO APPLY DIRECT POTENTIALS OF THE POLARITY TO EMIT LIGHT TO SCREEN ELEMENTS SELECTED TO EMIT LIGHT, WHILE MAINTAINING THE POTENTIAL ACROSS NON-SELECTED ELEMENTS AT THE OTHER POLARITY SO AS NOT TO EMIT LIGHT. 